Photoredox Radical/Polar Crossover Enables Construction of Saturated Nitrogen Heterocycles

Photoredox-mediated radical/polar crossover (RPC) processes offer new avenues for the synthesis of cyclic molecules. This process has been realized for the construction of medium-sized saturated nitrogen heterocycles. Photocatalytically generated alkyl radicals possessing pendant leaving groups engage imines in C-C bond formation, and subsequent reduction of the intermediate nitrogen-centered radical triggers anionic ring closure. With the aid of visible light irradiation, substituted pyrrolidines, piperidines, and azepanes can be prepared under mild, redox-neutral conditions.